U.S. Philips Corporation

Antonius H Peels

Jan Gerritsen

Jan Bijma

Antonius J Van Den Beld

The astigmatism of the electron beams (6, 7, 8) generated by an electron gun system (5) are substantially reduced by constructing the lens electrode components (25, 26) between which a focusing lens is formed in an operating electron gun to be inverted replicas of each other. The lens electrode components should be provided with the corresponding sides (45, 46) facing each other and with the corresponding apertures (38, 42) opposite to each other.

Color display tube

A field correction element (30) is provided in the peripheral field of a focusing lens of an electron gun system of a color display tube to reduce the potential differences between the electrodes of the focusing lens necessary for horizontal and vertical focusing, respectively. The field correction element (30) consists of a plate (31) which extends substantially perpendicularly to the electron beams and has elongate or square apertures (32, 33, 34) through which the electron beams (6, 7, 8) pass. It is also possible to perform convergence corrections by means of such a field correction element.

A color display tube has an electron gun system (5) with focusing lens electrodes (25, 26) producing overlapping lens fields. Correction of the overlapping lens fields is accomplished by means of at least one field correction plate (35, 36) which extends substantially perpendicularly to the beam axes and has elongate and/or square apertures (38, 39, 40) through which the electron beams pass.

Color display tube wtih overlapping field lens having a field correction

The spot quality of an electron beam produced by an electron gun in a cathode ray tube is improved by optimizing the dimensions of a beam-forming, apertured electrode arrangement in the gun. This arrangement includes electrodes for forming a cross-over followed by, in the direction of propagation of the electron beam, first and second lens electrodes centered around an axis, for defining an accelerating and prefocusing lens and at least two lens electrodes for defining a main focusing lens. The diameter of the aperture in the second lens electrode is smaller than twice the diameter of the aperture in the first lens electrode, and the effective spacing S-eff between the first and the second lens electrodes is smaller than 1 mm. S-eff is defined as the minimum of the function ##EQU1## where .DELTA.V is the operating voltage difference between the second and first lens electrodes and

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Eindhoven, Netherlands

Antonius H Peels